Two smaller muscles, the triceps and biceps, operate over a smaller range of contractile strains (12–23%), reflecting their role in controlling wing shape through elbow flexion and extension.

Both muscles are activated while being lengthened or undergoing nearly isometric force development, enhancing the work they perform during subsequent shortening. An emergent property of the primary flight muscles, consistent with their need to produce considerable work by moving the wings through large excursions during each wing stroke, is that the pectoralis and supracoracoideus muscles shorten over a large fraction of their resting fibre length (33–42%). Here, I review the function and architecture of key flight muscles related to how these muscles contribute to producing the power required for flapping flight, how the muscles are recruited to control wing motion and how they are used in manoeuvring. Muscles also produce substantial power during swimming, but this is mainly to overcome body drag rather than to support the animal's weight. This is in contrast to terrestrial locomotion, which offers mechanisms for minimizing energy losses associated with body movement combined with elastic energy savings to reduce the skeletal muscles' work requirements. Bird flight muscles, particularly at smaller body sizes, generally contract at high frequencies and do substantial work in order to produce the aerodynamic power needed to support the animal's weight in the air and to overcome drag. Flapping flight places strenuous requirements on the physiological performance of an animal.

Hummingbird exceed power suite 2008